Data Communication Using Light
Remote communication units using light have been conventionally known. A conventional communication unit using light generally encodes data using a combination of time durations of light intensity (flashing, blinking, etc.) and transmits it.
The present inventors uniquely developed an invention of encoding data using a color change (hue change, color phase change) instead of flashing or blinking and already filed a separate patent application.
Particularly, the present inventors are inventing a mechanism capable of transmitting the position of a light emitter while displaying data using the light emitter, the color of which changes in a specific pattern.
Tracking of Shape and Color
As described above, the present inventors are proposing a technology for representing data by a color change and indicating a position by the color change.
For the detection of the indicated position, there is used a technology for extracting and selecting a definite shape or a color change from a still image by an image processing technology. In the case of a moving light emitter, there is used a technology for tracking a definite shape or a color change from moving images.
Particularly, in the case of moving images, the light emitter is tracked by taking differences between respective still images constituting the moving images or extracting a color distribution characteristic.
Problems
However, there are the following problems to be overcome.
(1) To represent information, flashing and a color change need to be able to follow various patterns. To represent various data, flashing and the color change also need to change in various patterns.
(2) On the other hand, to detect the position of a light emitter, features of images used for a tracking technology need to be fixed. In other words, an object to be tracked generally needs to be in a fixed pattern.
As described above, the representation of various data and the detection of positions are generally contradicting events, and a technology for enabling tracking, specifying positions in images and analyzing data represented by its light emission pattern using only light images has been little known thus far.
For example, for the indication of a position, data representing the position needs to be a fixed given value to specify the position.
If the fixed value can be set, it is also possible to use a static optical automatic recognition code such as a bar-code symbol. In other words, each still image in moving images is extracted, a bar-code pattern is searched, analyzed and decoded for each still image to obtain raw data. With a technology capable of static analysis, even moving images can be complemented, with the result that raw data is analyzed (decoded) while the position is being detected by tracking.
Tracking on moving images is thought to be possible if a simple static pattern like a classic bar-code is used and representing data is fixed as described above.
On the other hand, a technology capable of tracking a pattern changing in a complicated manner on moving images is unknown. If it is ever tried to represent different types of data, a color pattern changes in a complicated manner, wherefore it is thought to be difficult in principle to track such a pattern.
If not a special camera, but a common general digital video camera generally used at present is used, this technology is thought to be widely usable for more general applications. Accordingly, we want to assume the use of a general video camera.
Under this assumption, at most moving images of about 30 fps can be obtained.
If it is possible to construct a system capable of data communication and position specification on the assumption of moving images of such quality, it goes without saying that a system having a high degree of convenience can be provided and applied for a variety of purposes.
The present invention was developed against such a background and one object thereof is to provide a system capable of tracking an object while realizing a practical data transfer amount.
Optical Automatic Recognition Code
Mechanisms which simply try to represent fixed data without considering a position have been conventionally widely known, and one of them is an optical automatic recognition code such as a bar-code. There are numerous purposes for attaching predetermined data such as an. ID to a good (called an object to be printed). Classically, the above optical automatic recognition codes such as bar-codes have been widely used.
In recent years, RFID using electromagnetic waves and the like have been also utilized. A predetermined mark is optically read from an optical recognition code to obtain raw data, and data can be read if the code is present in a visible range. Further, raw data is read from an RFID using electromagnetic waves and the RFID has a feature of being readable even if it is visually hidden.
A point-of-sale (POS) system used, for example, in stores and the like generally uses optical automatic recognition codes for goods. Bar-codes described above and color bar-codes are used as the optical automatic recognition codes. A bar-code is a two-color code composed of white bars and black bars. Various optical recognition codes utilizing many colors (red, blue, yellow, etc.) including chromatic colors have been and are being proposed.
The inventors of the present invention also proposed a color bar-code called a “1D color bit code” in patent applications (Japanese Patent Application 2006-196705, etc.).
Terms
An optical recognition code including chromatic colors is called a “color bar-code” for the sake of convenience. Further, if a code is simply called a “bar-code”, it means a classic bar-code composed of white bars and black bars.
An optical recognition code is generally attached to an object or its container or package in many cases. This act of attachment is called “marking”.
A body or means which embodies a mark by marking is generally called a “medium”. For example, “ink” used at the time of marking an optical recognition code on an object is a preferable example of a medium. If an object is an article of clothing or the like, a “tag” or the like made of thick paper is used and an optical recognition code such as a bar-code is attached to this tag in many cases. In such a case, the “tag” is a preferable example of a medium. An object may be particularly called an “object to be printed”. Particularly, this derives from the fact that objects were often recognized as “objects to be printed with bar-codes” (=objects to be printed) since bar-codes have been conventionally marked by printing in many cases.
Example Other than light
Although an optical recognition code represents data using “light”, means for representing data using another physical means are also known.
For example, automatic recognition means using radio waves such as the RFID described above has been developed and put to practical use. Non-contact IC card tickets of railways and the like are known as examples using this RFID.
Communication Examples
A field of a data “communication” technology exists as a technology relating to a technology for “displaying” data. In light of this data communication technology, many examples using other physical means are known.
For example, optical communication using optical fibers is known as a means using light similar to optical recognition codes. Although it is simply said to use “light”, there are known communication means using various lights such as infrared light, laser light and visible light as intermediaries.
Position Tracking
It has been conventionally known to use an optical recognition code not only for the purpose of “displaying” data, but also for the purpose of tracking the “position” of an object.
Such a purpose includes a position measurement/data communication system using infrared light as an intermediary, for example, as disclosed in the following prior art documents (patent documents 1, 2).
Prior Art Documents
Patent document 1 below discloses a position measurement/data communication system which includes a light emitting member for position display and a light emitting member for data transmission, photographs light emitting states of the members by an image pickup unit, measures a position based on the photographed images and conducts data communication by blinking the light emitting members.
Patent document 2 below discloses a position detection system which includes a marker and an individual identification code output unit, transmits an individual identification code by infrared light, electromagnetic waves or the like and changes the luminance/color phase of the marker in a predetermined pattern simultaneously with the transmission of this individual identification code, thereby determining the position of an individual object simultaneously with reception of the individual identification code.    Patent Document 1:
Japanese Unexamined Patent Publication No. 2001-208511    Patent Document 2:
Japanese Unexamined Patent Publication No. 2004-226227